30-30, 30-06, 45-70 etc.

Firehole Hunter

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This is probably the wrong place to post this thread and if needed to be moved so be it. But I have always wondered what the 2nd group of numbers referenced in the calibers as noted in the title meant. Is it the amount of powder or some other measurement or what?
 

OXN939

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Above is correct. Specifically, with .30-30 and .45-70, the second number quantifying powder volume is in reference to blackpowder.
 

16Bore

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I reckon back in the day it was pretty easy shopping for components!
 
OP
Firehole Hunter

Firehole Hunter

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Let me ask how much of smokeless powder is in the shells today instead of the black powder and compare that with a 7mm magnum cartridge.
 

smith406

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To expand the second number may also reference case length, ex. 5.56x45 or 7.62x51, or parent cartridge, ex. 6.5-.284.
 

16Bore

WKR
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I can only think of one firearm that doesn’t have a numerical designation in its name (22LR, 12Ga, 308 Win, etc.)

Anyone wanna guess?
 

ODB

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To expand the second number may also reference case length, ex. 5.56x45 or 7.62x51, or parent cartridge, ex. 6.5-.284.

Unless you talk about the nitro express cartridges where the second number is the bullet diameter (or close to it)

e.g. 500/465, 500/416, 450/400, 500/450, 400/360, etc
 

HRH2K

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Let me ask how much of smokeless powder is in the shells today instead of the black powder and compare that with a 7mm magnum cartridge.
I load my 45-70 with 47 grains of smokeless under a 405 grain bullet. Lighter bullets in 45-70 can use up to about 55 grains of smokeless. A normal 30-30 load uses about 30-40 grains of smokeless. I think the 30-30 was designed for use with smokeless powder, so the second “30” may reflect the original smokeless powder charge.
7mm mag would use probably 60-75 grains of smokeless depending on the bullet weight.
 
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